Circuit Breaker
【Function】What is a Miniature Circuit Breaker (MCB)?
An MCB is an automatic electrical protection device designed to protect circuits from overload and short-circuit conditions. It disconnects the circuit when a fault is detected and is commonly used in residential, commercial, and industrial power distribution systems.
【Function】What are the main functions of an MCB?
Overload protection : Trips when the current exceeds the rated level for an extended time.
Short-circuit protection : Trips instantly when a sudden, large current surge occurs due to a short circuit.
【Function】How is an MCB different from a fuse?
| Feature | MCB | Fuse |
| Resettable | V， Yes | X，No (must replace) |
| Reusability | High | Single-use only |
| Accuracy | Stable and reliable | Less precise |
| Cost | Higher initial cost, but reusable | Low initial cost |
【Function】What do the C, and D curves on an MCB mean?
These curves represent the trip characteristics, with C/D corresponding to different multiples of the rated current trip.
【Function】How does an MCB work?
An MCB uses two mechanisms:
Thermal trip unit : A bimetallic strip bends due to heat from overload and trips the circuit.
Magnetic trip unit : A magnetic coil activates instantly during a short circuit and trips the breaker.
【Product】How do I choose the correct rated current for an MCB?
Choose based on total circuit load, cable size, and load type. It's recommended to consult a professional or use electrical design guidelines.
【Product】What pole options are available for MW MCBs?
Currently, the 2P and 3P series are our primary recommendations.
【Product】What is the typical service life of MW MCBs?
According to IEC standards, the Mechanical life is approximately 10,000 operations.
【Product】Can MCBs be installed horizontally or upside down?
Most modern MCBs support horizontal installation, but vertical mounting is preferred for optimal performance and heat dissipation. Check the manufacturer’s datasheet for orientation guidelines.
【Product】Can multiple MCBs be connected in parallel?
Not recommended. Paralleling MCBs to increase current capacity can lead to uneven tripping and safety hazards.
Use properly rated devices instead.
【After-Sales】How do I know if the MCB has tripped?
The handle will move to the middle or OFF position. Before resetting, inspect the circuit for any faults. Once confirmed safe, manually switch it back to ON.
【After-Sales】Can an MCB be used as a regular ON/OFF switch?
Not recommended. MCBs are designed for protection, not for frequent switching. Repeated manual use will reduce mechanical life.
【After-Sales】Why does my MCB trip frequently?
Common causes include : Overloaded circuit、Short circuit or fault in wiring、Faulty connected equipment、Wrong MCB selection (rating or curve type).
【After-Sales】Does an MCB provide earth leakage (residual current) protection?
No. MCBs only protect against overload and short circuits. For earth leakage protection, use RCCB (Residual Current Circuit Breaker) or RCBO (combination of MCB + RCCB).
【After-Sales】What should I keep in mind when using MCBs?
Select appropriate rating and trip curve.
Regularly inspect terminals and contacts.
Avoid using as a switch.
Investigate frequent trips instead of resetting blindly.